IOP Conference Series: Materials Science and Engineering PAPER OPEN ACCESS Aspen HYSYS Simulation for Biodiesel Production from Waste Cooking Oil using Membrane Reactor To cite this article: Y B Abdurakhman et al 2017 IOP Conf. Ser.: Mater. Sci. Eng. 180 012273 View the article online for updates and enhancements. This content was downloaded from IP address 46.3.200.73 on 15/02/2018 at 09:56
International Conference on Recent Trends in Physics 2016 (ICRTP2016) Journal of Physics: Conference Series 755 (2016) 011001 doi:10.1088/1742-6596/755/1/011001 Aspen HYSYS Simulation for Biodiesel Production from Waste Cooking Oil using Membrane Reactor Y B Abdurakhman, Z A Putra *, and M R Bilad Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 32610 Tronoh, Perak, Malaysia *zulfan.adiputra@utp.edu.my Abstract. Biodiesel is a promising energy alternative solution to cater the demand of clean sustainable energy sources. Conventional biodiesel production is done by transesterification method using stirred tank reactor and homogeneous base catalyst, then followed by purification process. However, there are some drawbacks associated with this method. They include soap formation, sensitivity to free fatty acid (FFA) content and purification difficulties. Due to these downsides, biodiesel production using heterogeneous acid catalyst in membrane reactor is proposed. This project is aimed to study the effect of FFA content and membrane separation effectiveness on FAME yield. Waste cooking oil, inorganic pressure-driven membrane and WAl is used as raw material, membrane and heterogeneous acid catalyst, respectively. Biodiesel yield formulation is derived from literature data and then used in an Aspen HYSYS process simulation. Early phase cost estimation shows that FFA content does not affect the estimated capital investment, while the membrane separation effectiveness does significantly. Future work will include its comparison with the conventional biodiesel production process. 1. Introduction The dramatic growth of global population leads to high demand of sustainable energy supply and great attention on waste treatment. Biodiesel appears to be one of the most promising and feasible energy sources and clean fuel as it emits less toxic pollutants and greenhouse gases than petroleum diesel. It can be used as a stand-alone or blended with conventional diesel. It is also proven to be compatible for diesel engines without any required special modifications and will result no negative impacts to operating performance of the engines. Apart from the demand of sustainable energy, pollution issue is also important to be recognized. One of the key approach to minimize pollution is by recycling the waste into valuable products. Waste cooking oil is one of polluting materials which increases with human population. Hence, due to its abundance and low cost, waste cooking oil is going to be used as the raw material of biodiesel production. The current technologies of biodiesel production are based on micro-emulsion [1], pyrolysis [2] and transesterification [3]. Out of these methods, transesterification is the most commonly applied method in the industry with feedstocks varying from virgin oil (e.g.: canola oil, vegetable oil, olive oil, etc), used oil, animal fats and micro-algal oil. Conventional biodiesel production is done by transesterification method using stirred tank reactor and homogeneous catalyst, then followed by purification process. Homogeneous base catalysts are commonly used in biodiesel production due to Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by Ltd 1
its fast reaction rate and availability. However, the drawback of using this type of catalyst is its sensitivity to FFA content in the oil. This will lead to soap formation, hence decrease the biodiesel yield and cause purification difficulties [4]. On the other hand, conventional acid catalyst for producing biodiesel has been known to have a very long residence time. Therefore, biodiesel production from waste cooking oil using heterogeneous acid catalyst in membrane reactor is proposed. This option is considered to intensify the reaction and separation processes into a single reactor. The produced biodiesel or fatty acid methyl ester (FAME) can be drawn from the reactor simultaneously while retaining the unreacted oil. This situation then shifts the equilibrium reaction to the biodiesel side. This method will also remove the need of water to wash off the product from any impurities as required by the conventional production process. Thus, the purpose of this study is analysis the techno-economic feasibility of biodiesel production by using a heterogeneous acid catalyst membrane reactor. In the current study, the FFA content and the membrane separation effectiveness are evaluated. Their impacts are then evaluated by using an in-house capital cost estimationt tool. 2. Process description 2.1. Membrane reactor selection Transesterification process of biodiesel production can be carried out in various reactors such as batch, plug flow, fixed bed or continuous stirred-tank reactors. Batch reactor for commercial biodiesel production is not recommended because of its tedious mode of operations [5]. Thus, plug flow reactors, CSTR and fixed bed reactors are more viable to be used in commercial biodiesel production. However, some challenges ranging from poor biodiesel yield [5] to mass transfer limitation [6] are associated with these reactors. Membrane reactor is proven to be more environmentally friendly because it minimizes the waste water production [7]. Furthermore, membrane reactors are able to intensify the process and selectively remove the products throughout the process. Hence, it improves the product purity [5]. Membranes are generally classified into three groups; inorganic, organic and combination of both. Among those groups, inorganic membranes, such as metallic, ceramic or zeolitic membranes, are the most preferred due to their ability to withstand high temperatures, high acidic or basic environments [5]. Similarly, Barredo- Damas et al. [8] noted that beside of its high chemical, thermal and mechanical resistance, the cost of ceramic membranes has decreased. 2.2. Catalyst selection Catalyst is one of the most important factors in biodiesel production which will affect the reaction rate, operating conditions and yield. Lam et al. [4] stated that heterogeneous and enzymatic catalyst are the most suitable catalyst for transesterification of low quality feedstocks. It is due to their insensitivity to FFA and the downstream separation are relatively easy. However, enzyme catalyst is less preferable because of its sensitivity to methanol, very slow reaction rate and high cost [4]. In addition, heterogeneous base catalyst is also sensitive to FFA and will form soap if the FFA content is greater than 2 wt% [4]. Therefore, heterogeneous acid catalyst is the most preferable catalyst for waste cooking oil transesterification process. Among variety options of heterogeneous acid catalyst, synthesized tungsten on alumina supported catalyst (WAl) appears to be the most effective catalyst. Komintarachat and Chuepeng [9] shows that 1 wt% WAl loading and 0.3 methanol/wco weight ratio give 97.5 wt% FAME yield at 383 K in 2 hours from WCO containing 15 wt% FFA. 2.3. Reaction data Esterification and transesterification processes is widely used to produce biodiesel. The general reaction is represented in Figure 1. 2
(a) (b) Figure 1. General reaction to produce biodiesel, (a) transesterification reaction from triglyceride, (b) esterification reaction from fatty acids The desired product of this reaction is the methyl esters (biodiesel), while the by-product is glycerol. Impurities include leaching of heterogeneous acid catalyst or soap if basic catalyst is used [4]. The waste produced by biodiesel production is mainly water from the purification process. Komintarachat and Chuepeng [9] has studied the effects of WAl catalyst loading, methanol to oil weight ratio, temperature and time on ester yield. Based on their study, it is found that FAME yield is represented by Equation 1, obtained via developing statistical model: FAME Yield (wt%)= 7.1609 1326.6326 12.5697 2 0.0186 2 3.9446 2 321.9353 2 +0.0712 +3.5161 +0.5940 R (1) Where T, t, C and R represent reaction temperature (K), reaction time (hour), WAl catalyst amount (wt%) and methanol/wco weight ratio, respectively. 3. Process simulation 3.1. Fluid package and components The flowsheet for biodiesel production using membrane reactor is developed in Aspen HYSYS version 8.8 using NRTL fluid package. The composition of free fatty acids is taken from Wen et al. [10] while composition of triglycerides is assumed. FFA content of 15 wt% is assumed in the base case. Table 1 shows the composition of waste cooking oil as per base case design. Table 1. Typical composition of waste cooking oil as basecase design Components Mass Fraction Tripalmitin 0.074 Tristearin 0.027 Triolein 0.184 Trilinolein 0.478 Trilinolenin 0.051 Other TG 0.036 Palmitic Acid 0.013 Stearic Acid 0.005 Oleic Acid 0.032 3
Linoleic Acid 0.083 Linolenic Acid 0.009 Other FFA 0.006 H 2 O 0.003 3.2. Simulation environment Early phase process evaluation method is followed in this study to design the process and its evaluation [11]. Waste cooking oil and methanol are pumped and heated to 383.1 K and 11.51 bar before being fed to the reactor. Membrane reactor is simulated using a series of conversion reactor and component splitter with recycle retentate stream. Conversion reactor is run with 96.54% triglycerides conversion and 92.34% FFA conversion. The conversions are calculated from FAME yield assuming the reaction temperature of 383 K, 1 wt% WAl catalyst loading, 0.3 MeOH/WCO weight ratio and reaction time of 2 hours. Membrane separation factor is assumed to represent inorganic pressure-driven membrane which separate the feed based on the molecular weight. Table 2 displays membrane separation factor as per base case design. Table 2. Membrane separation effectiveness as basecase design Components Permeate Retentate Triglycerides 0 1 Free fatty acids 0.30 0.70 Fatty acid methyl esters 0.35 0.65 Glycerol 0.90 0.10 Methanol 1 0 Water 1 0 Permeate stream, containing the biodiesel, is drawn from the membrane reactor while retentate is recycled back to the reactor. Permeate is then cooled to room temperature and immediately formed FAME-Rich phase and Glycerol-Rich phase [6]. Methanol in FAME-Rich phase is separated using distillation column, then recycled back to methanol storage tank. The bottom product of this distillation column is fed to second distillation column to separate FAME and FFA. FAME (biodiesel) is recovered in distillate stream of the second distillation column. Figure 2 shows the HYSYS model for biodiesel production using membrane reactor. Figure 2. HYSYS model for biodiesel production using membrane reactor 4
From this developed basecase, capital cost is estimated by using in-house capital cost estimation tool. Then, two uncertainties are varied in this study to see the significances of their effects. These are the FFA content and the membrane effectiveness separation. The FFA content is varied from 10 wt%, 15 wt% to 20 wt%. The membrane effectiveness separation is varied as shown in Table 3. Table 3. Membrane separation factors Components Feed Fraction in Permeate Case 3 Base Case Case 4 Triglycerides 0 0 0 Free fatty acids 0.20 0.30 0.40 Fatty acid methyl esters 0.25 0.35 0.45 Glycerol 0.80 0.90 1 Methanol 1 1 1 Water 1 1 1 4. Results and discussion The effects of the abovementioned uncertainties to the estimated capital cost or capital expenditures (CAPEX) are shown in Figure 3. It is shown that the FFA content does not affect the estimated CAPEX. On the other hand, the membrane effectiveness separation does significantly influence the estimated CAPEX. The better the product separation via the membrane reactor will simplify the size of the recycle stream and the downstream equipment. Hence, the estimated CAPEX is reduced by 10% compared to the basecase. And vice versa, the estimated CAPEX is increased by almost 20% with the worse product separation via the membrane reactor. Figure 3. CAPEX changes due to variations of FFA in WCO and membrane effectiveness separation 5. Conclusion and Future Works 5
The present study has shown techno-economic evaluation of early phase process design for biodiesel production from waste cooking oil with membrane reactor. Based on the developed reaction yield model from literature, a process production has been designed and simulated in Aspen HYSYS environment. An estimation of the required capital expenditure has been made with an in-house cost estimation tool. The effect of two uncertainties, namely the FFA content in the oil and the effectiveness of the membrane separation. The result shows that the FFA content does not significantly change the estimated capital cost, while the membrane separation does change the cost significantly. This study is an on-going project which will include more uncertainties to cover and its comparison with conventional biodiesel process from waste cooking oil. Uncertainties for the capital cost estimate, among others, and the comparison will be evaluated in the future study by using Monte Carlo simulation. References [1] A. S. Ramadhas, S. Jayaraj, and C. Muraleedharan, Use of vegetable oils as I.C. engine fuels A review, Renew. Energy, vol. 29, no. 5, pp. 727 742, Apr. 2004. [2] L. Brennan and P. Owende, Biofuels from microalgae A review of technologies for production, processing, and extractions of biofuels and co-products, Renew. Sustain. Energy Rev., vol. 14, no. 2, pp. 557 577, Feb. 2010. [3] M. Zabeti, W. M. A. Wan Daud, and M. K. Aroua, Activity of solid catalysts for biodiesel production: A review, Fuel Process. Technol., vol. 90, no. 6, pp. 770 777, Jun. 2009. [4] M. K. Lam, K. T. Lee, and A. R. Mohamed, Homogeneous, heterogeneous and enzymatic catalysis for transesterification of high free fatty acid oil (waste cooking oil) to biodiesel: A review, Biotechnol. Adv., vol. 28, no. 4, pp. 500 518, Jul. 2010. [5] I. M. Atadashi, M. K. Aroua, A. R. Abdul Aziz, and N. M. N. Sulaiman, Membrane biodiesel production and refining technology: A critical review, Renew. Sustain. Energy Rev., vol. 15, no. 9, pp. 5051 5062, Dec. 2011. [6] P. Cao, M. A. Dubé, and A. Y. Tremblay, High-purity fatty acid methyl ester production from canola, soybean, palm, and yellow grease lipids by means of a membrane reactor, Biomass Bioenergy, vol. 32, no. 11, pp. 1028 1036, Nov. 2008. [7] Z. Yaakob, M. Mohammad, M. Alherbawi, Z. Alam, and K. Sopian, Overview of the production of biodiesel from Waste cooking oil, Renew. Sustain. Energy Rev., vol. 18, pp. 184 193, Feb. 2013. [8] S. Barredo-Damas, M. I. Alcaina-Miranda, A. Bes-Piá, M. I. Iborra-Clar, A. Iborra-Clar, and J. A. Mendoza-Roca, Ceramic membrane behavior in textile wastewater ultrafiltration, Desalination, vol. 250, no. 2, pp. 623 628, Jan. 2010. [9] C. Komintarachat and S. Chuepeng, Solid Acid Catalyst for Biodiesel Production from Waste Used Cooking Oils, Ind. Eng. Chem. Res., vol. 48, no. 20, pp. 9350 9353, Oct. 2009. [10] Z. Wen, X. Yu, S.-T. Tu, J. Yan, and E. Dahlquist, Biodiesel production from waste cooking oil catalyzed by TiO2 MgO mixed oxides, Bioresour. Technol., vol. 101, no. 24, pp. 9570 9576, Dec. 2010. [11] Adi Putra, Z., "Early Phase Process Evaluation: Industrial Practices," Indonesian Journal of Science and Technology, vol. 1, no. 2, pp. 238-248, 2016. 6